Map displaying device

ABSTRACT

A map displaying device for displaying an accessible range in an arbitrary display form determined in accordance with the scale of a displayed map and/or with the running state of a vehicle is provided. The map displaying device includes: a display unit for displaying map information stored in a map database; a search unit for calculating travel time information regarding a travel time to an arbitrary point accessible from a reference point; and a time information drawing unit for displaying the travel time information in a superimposed manner on the display unit by varying a display form in accordance with the scale of a map and/or with the running state of a user&#39;s vehicle.

This application is a continuation of application Ser. No. 12/065,364,filed Feb. 29, 2008, now U.S. Pat. No. 7,962,280, which is the NationalStage of International Application No. PCT/JP2006/318001, filed Sep. 11,2006.

TECHNICAL FIELD

The present invention relates to a map displaying device, andparticularly to a map displaying device for displaying an accessiblerange, accessible within an arbitrary time determined in accordance withthe scale of a displayed map and/or with the running state of a user'svehicle.

BACKGROUND ART

In recent years, a navigation device capable of displaying, based on mapinformation stored in an HDD or a DVD, a map of the neighborhood of theposition of a user's vehicle or a map of the vicinity of a predeterminedposition, along with landmarks, traffic information, and the like on adisplay of the device is widely used. In such a navigation device, whena user sets a destination, a search is performed for an appropriateroute to the destination and also the travel time for the travel iscalculated, whereby it is possible to present the resultant informationto the user.

In such a navigation device, a technique is proposed for displaying, onan optimal scale, a map which displays accessible positions, accessiblein all directions from the current position within a time set by a user(see Patent Document 1, for example).

Further, in an accessible range displaying device used for a carallocation/command system of a taxi, a security company or the like, atechnique is proposed for displaying a range accessible from the currentposition within a certain amount of time, by drawing a smooth curvearound the range in an amoeba-like manner (see Patent Document 2, forexample).

-   Patent Document 1: Japanese Patent Publication No. 3385657-   Patent Document 2: Japanese Laid-Open Patent Publication No.    11-16094

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, the navigation device disclosed in Patent Document 1 merelydisplays, on the optimal scale, an accessible range, accessible within atime set by the user, and cannot display an accessible range, accessiblewithin an arbitrary time determined in accordance with the scale of adisplayed map and/or with the running state of a user's vehicle.

Further, the accessible range displaying device disclosed in PatentDocument 2 merely displays in an amoeba-like manner an accessible range,accessible within a certain amount of time, and cannot display anaccessible range, accessible within an arbitrary time determined inaccordance with the scale of a displayed map and/or with the runningstate of a vehicle.

The present invention is directed to solving the above problems. Thatis, an object of the present invention is to provide a map displayingdevice for displaying an accessible range in an arbitrary display formdetermined in accordance with the scale of a displayed map and/or withthe running state of a vehicle.

Solution to the Problems

Aspects of the present invention are directed to a map displayingdevice. The present invention includes: display means for displaying mapinformation stored in a map database; search means for calculatingtravel time information regarding a travel time to an arbitrary pointaccessible from a reference point; and time information drawing meansfor displaying, in a superimposed manner on a map displayed on thedisplay means, the travel time information by varying a display form inaccordance with a scale of the map and/or with a running state of auser's vehicle.

Further, it is preferable that search condition determining means fordetermining a search condition in accordance with the scale of the map,with the running state of the user's vehicle, and/or with userinformation is further included, and that the search means calculates,using the search condition determined by the search conditiondetermining means, the travel time information regarding a travel timeto an arbitrary point accessible from a reference point.

Further, it is preferable that the search condition is a search range,which is a range of points to which travel times are to be calculated,and/or road types to be used for a search.

Further, it is preferable that the time information drawing meansdisplays the travel time information by connecting, by a line, points ofthe same travel time to one another or points of the same travel timeperiod to one another.

Further, it is preferable that the time information drawing meansdisplays the travel time information by dynamically changing the traveltime information such that the number of the lines displayed on thedisplay means is a constant number.

Further, it is preferable that the time information drawing meansdisplays, as a zone, the travel time information indicating a rangeaccessible within a certain travel time or within a certain travel timeperiod.

Further, it is preferable that the time information drawing meansdisplays, when displaying a plurality of the zones, the plurality of thezones by a gradation.

Further, it is preferable that the time information drawing meansdisplays the travel time information by drawing a road and/or anintersection in various display forms in accordance with the travel timeor a travel time period.

Further, it is preferable that the time information drawing meansdisplays the travel time information by changing an interval betweendisplayed travel times such that the wider the scale of the map is, thelonger the interval is.

Further, it is preferable that the time information drawing meansdisplays travel time information by changing an interval betweendisplayed travel times or between displayed travel time periods suchthat the slower the traveling speed of the user's vehicle is, the longerthe interval is.

Further, it is preferable that the time information drawing meansdisplays the travel time information by sequentially drawing, in aradiating manner, travel times or travel time periods in accordance withlarge/small relationships among the travel times or among the traveltime periods, respectively.

Further, it is preferable that the time information drawing meansdisplays the travel time information by performing drawing effectsdifferent between the inside and the outside of a line indicating apredetermined travel time or of a zone indicating a predetermined traveltime period.

Further, it is preferable that input means for inputting an instructionis further included, and that the travel time information specified bythe input means is changed to the travel time information regarding atravel time or a travel time period determined in accordance with aninstruction, inputted by the input means, to move an arbitrary point.

Further, it is preferable that the input means is a touch panel suchthat the time information drawing means displays the travel timeinformation specified by the touch panel, as the travel time informationregarding a travel time or a travel time period determined in accordancewith a pressed position moving across the touch panel.

Further, it is preferable that a slider bar capable of changing thedisplayed travel time information is displayed on the display means, andthat the time information drawing means displays the travel timeinformation determined in accordance with a setting, set by the inputmeans, of the slider bar.

Further, it is preferable that drawing/updating means fordrawing/updating the travel time information drawn by the timeinformation drawing means is further included, and that drawing/updatingis performed at timing at which the drawing/updating means the positionof the user's vehicle has passed through a node, at timing at which apredetermined time has passed, and/or at timing at which trafficcongestion information has been received.

Further, it is preferable that display controlling means for controllingarrow display indicating traffic congestion occurring on a road isfurther included, and that while the time information drawing means isdisplaying the time information in a superimposed manner, the displaycontrolling means controls the arrow display indicating trafficcongestion occurring on a road.

Further, it is preferable that further included are: input means forreceiving an input of a POI (point-of-interest) search condition to beused to perform a search for POI; recommended POI extracting means forextracting, based on the POI search condition received by the inputmeans, one or more recommended POI in descending order of recommendationlevel; and recommended POI display means for displaying, with the traveltime information drawn in a radiating manner by the time informationdrawing means, the one or more recommended POI in order of beingextracted by the recommended POI extracting means.

Further, it is preferable that route blinking display means fordisplaying, in a blinking manner, a route to each of the recommended POIextracted by the recommended POI extracting means is further included.

Further, it is preferable that the recommended POI extracting meansextracts one or more recommended POI in order of temporal proximity.

Further, it is preferable that the recommended POI extracting meansextracts one or more recommended POI in ascending order of evaluationvalue obtained by performing weighted addition on a distance from acurrent position, a travel time from the current position, and/or avalue obtained by quantifying a direction from the current position.

Further, it is preferable that access history storage means for storingaccess history of accessing POI is further included, and that therecommended POI extracting means extracts, with reference to the accesshistory stored in the access history storage means, one or morerecommended POI in descending order of frequency of access.

Effect of the Invention

As described above, according to the aspects of the present invention,it is possible to provide a map displaying device for displaying anaccessible range in an arbitrary display form determined in accordancewith the scale of a displayed map and/or with the running state of avehicle.

That is, since the present invention displays, on an ordinary andfamiliar map, travel time information represented by the travel time toan arbitrary point and the travel time between arbitrary points, inaccordance with the scale of the displayed map and with the runningstate of a vehicle, it is possible to present to a user a geographicaldistance and a temporal distance in an easily understandable manner.

Further, the present invention determines a search condition inaccordance with the scale of the map, with the running state of a user'svehicle, and/or with user information, and displays, in a superimposedmanner on the map, the travel time information regarding the traveltimes to points accessible from a reference point within a certainamount of time, by using the determined search condition. Thus, since itis possible to determine an appropriate range to search and aclassification of road types even in a state where the user does notselect only one destination, it is possible to reduce processing loadgenerated by searching an unnecessary range. Thus, in addition, sincethe present invention displays information regarding the travel times toarbitrary points, in a display form based on the appropriate range tosearch and the classification of road types in a superimposed manner onthe map representing the geographical distance, it is possible toappropriately present to the user the geographical distance and thetemporal distance to each point.

Further, a navigation device currently in practical use displays trafficinformation, which is provided by floating car data, as color-codedarrows on roads. However, when in the future, detailed trafficinformation which is typified by floating car data, Infrastructure andTransport and which includes narrow streets is available in a vehicle,the traffic information represented as local collections of arrows mayproduce a problem that a map displayed on a display screen iscomplicated and disorganized. According to the present invention,however, it is possible to solve a problem that a map displayed on adisplay screen is so complicated and disorganized as to confuse theuser.

Further, since the present invention draws appropriate travel timeinformation to indicate an appropriate accessible range in anappropriate display form in accordance with the scale of the map and/orwith the running state of the user's vehicle, it is possible toappropriately present to the user the geographical distance and thetemporal distance with high visibility.

Further, since the present invention performs a drawing effect ofdisplaying the travel time information in a radiating manner, it ispossible to present to the user the travel time information by asuccessive and small unit in an easily understandable manner.

Further, since the present invention draws/updates the travel timeinformation at appropriate timing, it is possible to present to the userthe travel time information in real time even while driving.

Further, the present invention can display the travel time informationthrough input means such as a touch panel or a slider bar while a mapdisplayed on the display screen is being viewed. Thus, since the presentinvention can specify the displayed travel time information by anintuitive operation through the touch panel and the like, and thus canfine-tune the displayed travel time information, it is possible toeasily present to the user the travel time information with highvisibility.

Further, since the present invention displays a recommended POI with thetravel time information displayed in a radiating manner, it is possibleto present to the user the travel time to the recommended POI in aneasily understandable manner.

Further, since the present invention displays the route to therecommended POI in a blinking manner, it is possible to present to theuser the route to travel in an easily understandable manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a map displaying device according toan embodiment of the present invention.

FIG. 2 is a diagram showing an example of a map presented to a user.

FIG. 3 is a diagram showing tables stored in a map DB 101.

FIG. 4 is a diagram representing, by a network of nodes and links, roadsincluded in a map.

FIG. 5 is a table having stored therein, with respect to the scale of amap, information regarding road types to be used for map display.

FIG. 6 is a flow chart showing the flow of a process performed by themap displaying device according to the embodiment of the presentinvention.

FIG. 7 is a flow chart showing a determination processing operation,performed by search condition determining means 107, of a first searchcondition.

FIG. 8 is a flow chart showing a determination processing operation,performed by the search condition determining means 107, of a secondsearch condition.

FIG. 9 is a conceptual diagram showing grids included in a map.

FIG. 10 is a diagram illustrating a calculation method of travel times.

FIG. 11 is a diagram showing a calculation method of a travel time to apoint provided on a link.

FIG. 12 is a diagram showing a state where isochronal lines, eachconnecting points of the same travel time to one another, aresuperimposed on a map.

FIG. 13 is a diagram showing a state where, as zones, ranges accessiblewithin certain travel times are superimposed on a map.

FIG. 14 is a diagram illustrating a drawing method of an isochronalzone.

FIG. 15 is a schematic diagram illustrating a drawing method for drawinga plurality of isochronal zones.

FIG. 16 is a diagram showing a state where roads vary in display formdetermined in accordance with travel times.

FIG. 17 is a diagram showing a state where intersections vary in displayform determined in accordance with travel times.

FIG. 18 is: (A) a diagram showing travel times indicated by isochronallines of a detailed map; and (B) a diagram showing travel timesindicated by isochronal lines of a wide-area map.

FIG. 19 is a flow chart showing an operation of controlling a displayform in accordance with the scale so as to improve the visibility ofdisplayed travel time information.

FIG. 20 is a flow chart showing an operation of controlling a displayform in accordance with the vehicle speed even when the scale is of thesame, so as to improve the visibility of displayed travel timeinformation.

FIG. 21 is: (A) a diagram showing a state where an isochronal line of10-minute travel time is displayed; (B) a diagram showing a state wherethe isochronal line of 10-minute travel time is erased and an isochronalline of 11-minute travel time is displayed; and (C) a diagram showing astate where the isochronal line of 11-minute travel time is erased andan isochronal line of 12-minute travel time is displayed.

FIG. 22 is: (A) a diagram showing a state where an isochronal line of10-minute travel time is displayed; (B) a diagram showing a state wherean isochronal line of 15-minute travel time is additionally displayedwithout erasing the isochronal line of 10-minute travel time; and (C) adiagram showing a state where an isochronal line of 20-minute traveltime is additionally displayed without erasing either of the isochronallines of 10-minute travel time nor 15-minute travel time.

FIG. 23 is: (A) a diagram showing a state where an isochronal line isspecified; (B) a diagram showing a state where the isochronal line isslid and another isochronal line is displayed; (C) a diagram showing astate where an isochronal line of 10-minute travel time is displayedusing a slider bar; and (D) a diagram showing a state where anisochronal line of 15-minute travel time is displayed using the sliderbar.

FIG. 24 is a flow chart showing an operation, performed by timeinformation drawing means 109, of drawing/updating travel timeinformation.

FIG. 25 is a flow chart showing an operation, performed by the timeinformation drawing means 109, of controlling arrow display indicatingtraffic congestion occurring on a road.

FIG. 26 is a flow chart showing an operation, performed by the timeinformation drawing means 109, of displaying travel time information ina radiating manner and also displaying a POI which is present betweenisochronal lines indicated by the travel time information and which istemporally closest to the current position.

FIG. 27 is a diagram showing a state where travel time information isdisplayed in a radiating manner and a POI which is present betweenisochronal lines indicated by the travel time information and which istemporally closest to the current position, is also displayed.

FIG. 28 is a diagram showing a state where travel time information isdisplayed in a radiating manner and a POI which is present betweenisochronal lines indicated by the travel time information and which istemporally closest to the current position, is also displayed.

FIG. 29 is a diagram showing a state where travel time information isdisplayed in a radiating manner and a POI which is present betweenisochronal lines indicated by the travel time information and which istemporally closest to the current position, is also displayed.

FIG. 30 is a diagram showing a state where travel time information isdisplayed in a radiating manner and POI each of which is present betweenisochronal lines indicated by the travel time information and each ofwhich is temporally closest to the current position, are also displayed.

DESCRIPTION OF THE REFERENCE CHARACTERS

-   -   101 map DB    -   102 traffic congestion information receiving means    -   103 position determining means    -   104 input means    -   105 display means    -   106 control means    -   107 search condition determining means    -   108 search means    -   109 time information drawing means    -   110 bearing mark    -   112 user's-vehicle-periphery equality range    -   113 traveling-direction-oriented range    -   114 traveling-road-type-oriented range    -   115, 116, 117, 118, 119, 120 closed curve

DETAILED DESCRIPTION OF THE INVENTION

With reference to the drawings, a map displaying device according to anembodiment of the present invention will be described below.

FIG. 1 shows a structure of the map displaying device according to theembodiment of the present invention. In the present embodiment,described is a case where the map displaying device is applied to anavigation device mounted on an automobile.

The map displaying device according to the present embodiment includes amap DB 101, traffic congestion information receiving means 102, positiondetermining means 103, input means 104, display means 105, and controlmeans 106.

The map DB 101 may be provided as, for example, an HDD or a DVD eachhaving stored therein map information such as data of roads andintersections. The present invention, however, is not limited thereto,and information to be stored in the map DB 101 may be downloaded asneeded from a traffic information center (not shown) by a communicationdevice (e.g., a mobile phone and a PHS) not shown in the figures.Further, the map information may be acquired not by directly accessingthe map DB 101 provided as the HDD or the DVD, but by referring to amemory which is provided in the map displaying device and into whichnecessary data of the data stored in the map DB 101 has been loaded inadvance.

As shown in FIG. 2, a map is presented to a user by the display means105 and represents information regarding a road width, a road direction,an angle at which roads intersect with each other, and the like. In FIG.2, 110 is a mark indicating bearings and 111 is a mark indicating theposition of a user's vehicle. Note that in general, not only theabove-described road information but also background data (a river, agreen space, etc.), POI information (e.g., landmark icons indicating afamily restaurant, a gas station, etc.), menu buttons, and the like arepresented to the user, but will not be described in the presentembodiment.

As shown in FIG. 3, the road information is stored in the map DB 101, asa node data table (A), a link data table (B), and a road-type data table(C). A node stored in the node data table (A) is a point, such as anintersection and a junction, at which a road splits in severaldirections. The node includes position information such aslatitude/longitude and also includes the number and link IDs of thebelow-described links connected to the node. A link stored in the linkdata table (B) represents a road connecting nodes to each other andincludes IDs of a starting-point node and an end-point node which arethe both ends of the link, a link length (in meters, kilometers, etc.),a link width (representing a road width in meters, etc.), and a roadtype. The link length is a reference for calculating the travel time totravel the road and is used as a cost value for performing a routesearch. Further, the value of the road type, which is one of theattributes of the link data table (B), can be identified by theroad-type data table (C), in which road types such as a first class road(EXPRESS WAY, HIGHWAY) and a fifth class road (GENERAL ROAD) have valuesdifferent from one another.

FIG. 4 is a schematic diagram showing a state where the road informationstored in the map DB 101 is constructed as a road network includingnodes and links. The road network constructed as described above may beused, whereby it is possible to calculate the route and the travel timeto a predetermined point by following the nodes and the links.

FIG. 5 is a table having stored therein, with respect to the scale of amap, information regarding road types used for map display, and thetable is stored in the map DB 101. Note that the table may be stored ina memory not shown in the figures or the like. The table indicates thatfor example, when a map having the scale of 3.2 km is displayed, thelinks belonging to the road types including a first class road, a secondclass road (URBAN EXPRESSWAY),

a third class road (MAJOR LOCAL ROAD), and a fourth class road(PREFECTURAI ROAD) are displayed on the display means 105, whereas thelinks belonging to the road types including a fifth class road, a sixthclass road (SLIP LAMP), and a seventh class road (NARROW STREET) are notdisplayed on the display means 105.

The traffic congestion information receiving means 102 employs variousdevices in accordance with the type (floating car data, etc.) of trafficcongestion information to be provided, and uses a receiving devicecompatible with an FM broadcast wave, an optical/radio beacon, a DSRC(Dedicated Short Range Communication) receiver, a mobile phone, and thelike. The present invention is not limited thereto, and alternatively,the traffic congestion information may be received from a trafficcongestion prediction database which is provided in the map DB 101 andhas stored therein past traffic congestion statistical data (data basedon a time of day, a day of the week, a date, and the like of the past).Note that traffic information is information indicating the travel timeto pass through a section of the link length included in the link datatable (B) and uses average speed data obtained in the section of thelink length, and the like. The traffic congestion information may beused, whereby the travel time is determined with high accuracy, takinginto account the degree of congestion.

The position determining means 103, attached to the vehicle on which themap displaying device is mounted, may be, for example, a GLASS (GlobalNavigation Satellite System) receiver, a vehicle speed sensor, a gyro(angular velocity) sensor, and an acceleration sensor, so as to measurethe current position, the speed, and the direction of the vehicle. TheGNSS receiver, which may be, for example, a GPS receiver, measures theabsolute position of the receiver by demodulating radio waves receivedfrom a plurality of satellites. Note that in order to measure thecurrent position, the speed, and the direction of the vehicle, the GNSSreceiver and the aforementioned various sensors may be used separatelyor combined.

The input means 104 may include, for example, a device having arrangedtherein a predetermined number of press switches, a device of atouch-panel type, or a remote control, each of which receives aninstruction from the user, or may include a microphone and a speechrecognition engine, which recognize the voice of the user and convertthe recognized voice into information to be inputted to the mapdisplaying device.

The display means 105 may be, for example, a liquid crystal display, aplasma display, or an organic electroluminescent display, eachdisplaying an image in accordance with display image data created by thecontrol means 106.

Next, the control means 106 will be described. The control means 106includes search condition determining means 107, search means 108, andtime information drawing means 109. The control means 106 calculates thetravel times for the user's vehicle to access a plurality of pointsprovided in a predetermined map area and presents the calculated traveltimes on the display means 105. Each component will be described indetail below.

Based on the scale of the map, the running state of the vehicle, and/oruser information, the search condition determining means 107 determinesthe range (i.e., a search range) of points to which the travel times areto be calculated, and the road types to be used for the search. In anordinary navigation device, only the travel time to a destinationspecified by the user may be calculated and the search range may be setbetween the starting point and the endpoint (the destination) of thesearch. However, since the present embodiment is directed to a statewhere the user does not select only one destination, the searchcondition determining means 107 performs a function of determining anappropriate area to search. Basically, the search range to be extractedincludes at least the map area displayed on the display means 105.Further, in the ordinary navigation device, the search is performedbased on the road types specified by the user (for example, an input foravoiding highways or avoiding toll roads may be performed). However,since in the present embodiment, the map displaying device is requiredto operate in a state where the user does not set any destination, themap displaying device determines, taking the state into account on itsown, the road types to be used.

Based on the search range and the road types which are determined by thesearch condition determining means 107, the search means 108 calculatesthe travel times to all possible points (routes) to travel from areference point (hereinafter, the current position of the user's vehiclewill be described as an example thereof) of the search start. The searchmethod may employ the heretofore known Dijkstra algorithm, in whichcase, however, the below-described various improvements are necessaryfor calculating the travel times.

The time information drawing means 109 has: a function of determining,based on travel time information regarding the travel time to each pointwhich is calculated by the search means 108, a drawing style of thetravel time information, and of displaying the determined drawing stylewith the map information on the display means 105; a function ofcontrolling a display form in accordance with the scale and the vehiclespeed so as to improve the visibility of the displayed travel timeinformation; a function of performing a drawing effect; a function ofchanging the travel time to an arbitrary travel time when receiving fromthe user an instruction to change the travel time; a function ofperforming drawing/updating; and/or a function of controlling arrowdisplay indicating traffic congestion occurring on a road. As examplesof the drawing style of the travel time information, the presentembodiment illustrates the following three drawing styles:

(1) displaying the travel time information as a line connecting, to oneanother, points to which the travel times from the reference point arethe same;

(2) displaying the travel time information as a zone collectivelyincluding points to which the travel times from the reference point arethe same; and

(3) displaying roads and/or intersections by varying the colors and thepatterns thereof in accordance with the range of the travel times fromthe reference point.

Particularly, the drawing style of (1) will be hereinafter referred toas an isochronal line. Further, the drawing style of (2) will behereinafter referred to as an isochronal zone. Note that it ispreferable that the user can select a drawing style from the drawingstyles (1) to (3), through a setting screen not shown in the figures.

With reference to FIG. 6, the flow of the overall process performed inthe map displaying device having the above structure will be described.FIG. 6 is a flow chart showing an operation performed until the traveltime information is drawn in a superimposed manner on the map.

First, an instruction to draw the travel time information is receivedfrom the user through the input means 104 (“Yes” in step S11). Then,when an instruction to specify the reference point of the search startis received through the input means 104 (“Yes” in step S12), the controlmeans 106 sets, with reference to the map DB 101, a specified point asthe reference point (step S13). When the instruction to specify thereference point is not received (“No” in step S12), the control means106 sets as the reference point of the search start a node or a linkwhich is closest to the current position, detected by the positiondetermining means 103, of the user's vehicle (step S14).

When the reference point is determined, the search condition determiningmeans 107 of the control means 106 determines the search range, the roadtypes to be used for the search, and the like, based on the scale of themap, the running state of the vehicle, the user information, and/or thelike (step S15). When a search condition is determined, the search means108 performs, using the determined road types, the route search for theroutes to points provided within the search range determined based onthe search condition, and calculates the travel times (step S16). Notethat the search is performed for roads and intersections as searchtargets unless otherwise specified, and the search is also performed,when a particular category of POI or landmarks are specified by theuser, for the specified particular category of POI or the specifiedlandmarks.

When the search is completed, the time information drawing means 109determines a drawing style of the travel time information to be drawn onthe map (step S17). Then, the time information drawing means 109performs functions, such as the function of controlling a display formin accordance with the scale so as to improve the visibility of thedisplayed travel time information and/or the function of performing adrawing effect, whereby the travel time information is drawn in asuperimposed manner on the map displayed on the display means 105 (stepS18).

Note that although in step S11, described is a case where the traveltime information is drawn in a superimposed manner on the map only afterthe instruction is received from the user, the present invention is notlimited thereto. The travel time information may be constantly drawn ina superimposed manner on the map when a destination is not set throughthe setting screen not shown in the figures.

Next, with reference to FIGS. 7 and 8, a detailed operation, performedby the search condition determining means 107, of determining the searchcondition in step S15 of FIG. 6 will be described.

FIG. 7 is a flow chart showing a determination processing operation,performed by the search condition determining means 107, of a firstsearch condition. FIG. 7 will be described with reference to FIGS. 3 and5. In the road-type data table (C) of FIG. 3, for convenience, the roadtypes will be referred to in such a manner that the closer to the top ofthe table, the higher rank the road type is of. For example, the firstclass road is the road type of the highest rank.

First, a road-type row (hereinafter referred to as an R1) used with thescale of the current map display is acquired from the table of FIG. 5(step S21). Then, the road type (hereinafter referred to as an R2) ofthe road currently being traveled by the user's vehicle is acquiredbased on a positioning result of the position determining means 103(step S22). In step S23, it is determined whether or not the R2 isincluded in the R1. When the R2 is included in the R1 (step S23: “Yes”),the R1 is set as the road types to be used for the search (step S24).For example, in FIG. 5, when the scale is of 1.6 km and the road type ofthe road being traveled by the user's vehicle is the fifth class road,the R1 is the first class road, the second class road, the third classroad, the fourth class road and the fifth class road, and the R2 is thefifth class road. In this case, the R1 is set as the road types to beused for the search. On the other hand, when the R2 is not included inthe R1 (step S23: “No”), the road types starting from the road type ofthe highest rank of the R1 to the road type of the R2 are set as theroad types to be used for the search (step S25). For example, in FIG. 5,when the scale is of 6.4 km and the road type of the road being traveledby the user's vehicle is the fifth class road, the R1 is the first classroad, the second class road and the third class road, and the R2 is thefifth class road. In this case, the first class road, the second classroad, the third class road, the fourth class road, and the fifth classroad are set as the road types to be used for the search. Then, thesearch range is determined (step S26). As described above, when awide-area map (having the scale of 400 m or more) is displayed on thedisplay means 105 and the road type of the road being traveled by theuser's vehicle is of a high rank (i.e., the road type is other than theseventh class road), seventh class roads are not to be displayed and arenot the roads to be currently traveled, and therefore may be removedfrom the search targets. The search range is determined such that whenthe current average speed of the user's vehicle is, for example, 500m/min. and the travel time to be obtained is, for example, 10 minutesand if the position of the user's vehicle is the point of the searchstart, all accessible points provided within a circle having a radius of5000 m and having the position of the user's vehicle as its center aredetermined as the search range.

FIG. 8 is a flow chart showing a determination processing operation,performed by the search condition determining means 107, of a secondsearch condition. FIG. 8 will be described with reference to FIG. 3. Inthe road-type data table (C) of FIG. 3, for convenience, the first classroad and the second class road will be referred to as the road types ofa first category, and the third class road, the fourth class road, thefifth class road, the sixth class road and the seventh class road willbe referred to as the road types of a second category.

The road type of the road currently being traveled by the user's vehicleis acquired based on a positioning result of the position determiningmeans 103 (step S31). Then, the road types of the same category as theroad type of the road currently being traveled by the user's vehicle areset as the road types to be used for the search (step S32). For example,when the road type of the road currently being traveled by the user'svehicle is the second class road, the road types of the first categoryare the road types to be used for the search. Further, when the roadtype of the road currently being traveled by the user's vehicle is thefifth class road, the road types of the second category are the roadtypes to be used for the search. Then, the search range is determinedbased on the determined road types (step S33). The search range may bedetermined such that for example, when the user's vehicle is traveling aroad included in the road types of the first category, the distancebetween crossroads is large in general and accordingly, possible roadsto be traveled by the user's vehicle are limited until the user'svehicle reaches a crossroads. Therefore, an area around the possibleroads may be clearly extracted as the search range.

Note that the search condition determining means 107 may not determinethe search range and the road types as described above, and the searchcondition determining means 107 may select roads to be search targetsbased on the user information. The user information may be, for example,information regarding the past travel history of the user and may bestored in storage means (a non-volatile memory) not shown in thefigures. From the information regarding the past travel history, travelcharacteristics such as, “rarely travels a narrow street”, “prefers totravel a wide road”, or “usually travels certain routine roads whentraveling in a predetermined direction”, may be extracted, and then thesearch range and the road types may be determined based on the abovecharacteristics.

Further, the search condition determining means 107 may extract rangesas shown in FIG. 9. The map information, managed in a grid manner asshown therein, may be presented to the user, for example, on a gridbasis. The user's-vehicle-periphery equality range 112 of FIG. 9includes, as the search range, 9 grids having as its center a grid inwhich the user's vehicle is present and also having 8 grids therearound.The traveling-direction-oriented range 113 of FIG. 9 clearly includes,as the search range, an area provided in the traveling direction of theuser's vehicle, that is, an area in which the map information and thetravel time information are likely to be necessary hereafter. Thetraveling-road-type-oriented range 114 of FIG. 9 shows an example of thesearch range used in a case where the road being traveled by the user'svehicle is present from the position of the user's vehicle to the upperportion of the map. As described above, the search condition determiningmeans 107 may set the position of the user's vehicle as the referencepoint of the search start, and may determine the search range inaccordance with the grid in which the user's vehicle is present and withthe state of the road network. Note that the shape of a grid may notnecessarily be rectangular as shown in FIG. 9, and may be in any shape.

Although the operation, performed by the search condition determiningmeans 107, of determining the search condition is described above, thepresent invention is not limited thereto. The search range may also bedetermined in accordance with the running state (the circumstancessurrounding the travel of the user's vehicle, such as the position, thespeed and the traveling direction of the user's vehicle, and the stateof traffic congestion) of the user's vehicle and the like.

Note that the reference point is not limited to the current position ofthe user's vehicle, and when the user specifies a search start positionin an explicit manner, the specified position may be the referencepoint.

Next, with reference to FIGS. 10 and 11, an operation, performed by thesearch means 108, of calculating, based on the search range and the roadtypes which are determined by the search condition determining means107, the travel times to all possible points (routes) to travel from thereference point (hereinafter, the current position of the user's vehiclewill be described as an example thereof) of the search start, will bedescribed. Note that it is assumed that nodes and links of FIG. 10 havebeen extracted as the search range by the search condition determiningmeans 107. Additionally, it is assumed that the current position of theuser's vehicle is present at a point which is provided on a link(represented as a “link AB”) connecting a node A to a node B and atwhich the cost from the node B is 3. In FIGS. 10 and 11, described is acase where the travel time to travel one section, which is allocated acost of 3, is 3 minutes, for convenience.

Based on the position of the user's vehicle as the reference point, thesearch means 108 calculates the costs of all of the links provided inthe range of FIG. 10. Note that a one-way road is not followed in abackward manner. The total cost between two points is represented by thesum of the costs of all of the links connecting the two points to eachother. Based on all of the calculated costs, arbitrary points accessiblefrom the position of the user's vehicle, for example, points of 5-minutetravel time, 10-minute travel time, 15-minute travel time, and 20-minutetravel time, each from the position of the user's vehicle, are extractedin FIG. 10.

The travel time from a node to another node is obtained by the sum ofthe costs of the links present therebetween, while the travel time to apoint provided on a link is calculated by a method shown in FIG. 11.When the travel times from the position of the user's vehicle to a nodeL and a node M are 18 minutes and 23 minutes, respectively, and the costof a link LM is 5, a point of 20-minute travel time can be viewed as apoint corresponding to two-fifths of the link LM. Further, as with anode C of FIG. 10, there exist a large number of points each accessiblevia a plurality of routes, to which points the travel times varydepending on the route. In this case, as the travel time to the node C,a smaller value (20 minutes) is selected. Note that the travel times maybe calculated with reference to the traffic congestion information, andconsequently, it may take a shorter time to travel a longer distanceroute.

Although in the above example, described is a case where a point towhich the travel time is calculated by the search means 108 is a node ora point provided on a link, an instruction may be received from the userthrough the input means 104. For example, when the user specifies“restaurants”, the landmarks corresponding to the category “restaurants”may be extracted from the landmarks provided within the range extractedby the search condition determining means 107, and the travel times tothe corresponding landmarks may be calculated.

Further, on the route for which the search is performed by the searchmeans 108, turning of the vehicle at a point other than an intersectionmay be taken into account. In FIG. 10, for example, the user's vehiclepresent on the link AB may not be required to reach the node B bytraveling the link from A to B, so as to turn, and may turn beforereaching the node B and travel the link from B to A. Thus, the searchmay be performed, taking into account the above-described route.

Further, the reference point of the search start is not limited to thecurrent position of the user's vehicle, and needless to say, anarbitrary point specified by the user can be set as the reference point.

Next, with reference to FIGS. 12 through 17, the function, performed bythe time information drawing means 109, of determining a drawing styleof the travel time information and of displaying the determined drawingstyle with the map information on the display means 105 will bedescribed.

FIG. 12 is a schematic diagram showing an example where isochronal linesof the drawing style (1) are drawn. The lines of FIG. 12 may be, forexample, calculated and drawn based on a drawing method of theheretofore known Bezier curve as disclosed in Patent Document 2 or basedon the below-described image processing. By the above-described process,points of 5-minute travel time, 10-minute travel time, and 20-minutetravel time, each from the position of the user's vehicle which isdetermined as the reference point, are drawn as closed curves. Note thatthe lines may be drawn not only by the drawing method of the Beziercurve but also by that of the heretofore known spline curve and thelike, and also may be drawn not only as closed curves but also as opencurves or as straight lines.

The isochronal lines may be drawn as described above on an ordinarilydisplayed map, and thus the user can verify the distances to a pluralityof landmarks provided on the map, on a distance basis, a time basis, andthe like at the same time, and it is useful for determining adestination. Further, drawing/updating may be performed at thebelow-described timing, and thus it is possible to verify in real timethe distance to a destination on a distance basis and a time basis evenwhile the vehicle is running.

Further, points to be connected by an isochronal line of the Beziercurve and the like may belong to the same travel time period. Whenpoints provided on links as shown in FIG. 11 are removed from thetargets and only nodes or only major intersections included therein arethe targets to be connected to draw an isochronal line, the travel timesmay not necessarily be of convenient numbers such as 5 minutes and 20minutes. In this case, the travel time period may have some range of thetravel times, such as 5-to-10-minute time period and 10-to-15-minutetime period, and accordingly, points of 12-minute travel time and14-minute travel time may be considered to belong to the same10-to-15-minute travel time period and may be connected to each other.

FIG. 13 is a schematic diagram showing an example where isochronal zonesof the drawing style (2) are drawn. As shown in FIG. 13, rangesaccessible within certain travel times are drawn as zones. The zones maybe drawn as described above, and thus it is useful since it is possibleto verify information regarding farthest points accessible from theposition of the user's vehicle and least distant points only accessiblefrom the position of the user's vehicle, each within a certain traveltime, e.g., 10 minutes. Particularly, in a state where trafficcongestion is locally occurring, the range of an isochronal zone tendsto increase in width, and therefore produces an effect of notifying theuser that it is better to set a destination than to travel withoutsetting any destination. In this case, the user may be notified of amessage for urging him/her to set a destination. In contrast, in a casewhere traffic congestion is not occurring, the range of an isochronalzone tends to decrease in width, and therefore the user can understandthat it is only possible to access points having similar distances fromthe user within a certain amount of time even by selecting and travelingany roads.

Next, with reference to FIGS. 14 and 15, a method of drawing anisochronal zone will be specifically described. In FIG. 14, a symmetricmap having as its center the position, represented as a star mark, ofthe user's vehicle is equally divided in m directions. Further, in eachof the directions 1 through m, a node closest in a straight line fromthe position of the user's vehicle is represented as a circle, while anode farthest in a straight line therefrom is represented as a square.The search is performed for the circle and the square by the searchmeans 108. Then, a closed curve 115 and a closed curve 116 are obtainedby connecting the circles to one another and the squares to one anotherbased on, for example, the drawing method of the heretofore known Beziercurve as disclosed in Patent Document 2. Then, an isochronal zone isdrawn by filling an area between the curve 115 and the curve 116. Notethat it is preferable that transparency processing is performed for theisochronal zone such that the map can also be viewed. Further, althoughin FIG. 14, m is set as 8, m may be changed to 4, 8, 16, 32, and thelike, whereby the representational accuracy of an area accessible withina predetermined time may be changed.

FIG. 15 is a schematic diagram illustrating a drawing method for drawinga plurality of isochronal zones. Similarly to FIG. 14, a symmetric maphaving as its center the position, represented as a star mark, of theuser's vehicle is equally divided in m directions. Further, in each ofthe directions 1 through m, nodes closest in a straight line from theposition of the user's vehicle are represented as circles (a node of10-minute travel time as an unfilled circle and a node of 20-minutetravel time as a filled circle), while nodes farthest in a straight linetherefrom are represented as squares (a node of 10-minute travel time asan unfilled square and a node of 20-minute travel time as a filledsquare). The circles and the squares are the search result obtained bythe search means 108. Then, closed curves 117, 118, 119, and 120 areobtained by connecting the unfilled/filled circles to one another,respectively, and the unfilled/filled squares to one another,respectively, based on the drawing method of the heretofore known Beziercurve as disclosed in Patent Document 2, for example.

As shown in FIG. 15, a closest node accessible within 20 minutes may behighly likely to be closer in a straight line to the position of theuser's vehicle than a farthest node accessible within 10 minutes is,depending on the configuration of the road network and the occurrencestate of traffic congestion. In this case, the isochronal zones arerepresented by a gradation. More specifically, when the area between theclosed curve 117 and the closed curve 119 is drawn in red (RGB=255, 0,0) and the area between the closed curve 118 and the closed curve 120 isdrawn in blue (RGB=0, 0, 255), the area between the closed curve 118 andthe closed curve 119 may be drawn in purple (RGB=127, 0, 127), which isthe color between red and blue. Thus, it is possible to successivelydraw a plurality of isochronal zones such as those of 10-minute traveltime and 20-minute travel time.

FIG. 16 is a schematic diagram showing an example of the drawing style(3) where roads (links) are drawn by varying the colors and the patternsthereof in accordance with the range of the travel times from thereference point. As shown in FIG. 16, the time information drawing means109 draws the roads by varying the colors and the patterns thereof inaccordance with the range of the travel times (e.g., the rangeaccessible within 5 minutes, the range accessible within 5 to 10minutes) to access the roads, without drawing isochronal lines norisochronal zones. Further, the time information drawing means 109 maydraw landmarks displayed on the map, by varying the colors and thepatterns thereof.

FIG. 17 is a schematic diagram showing an example of the drawing style(3) where intersections (nodes) are drawn by varying the colors and thepatterns thereof in accordance with the range of the travel times fromthe reference point. As shown in FIG. 17, the time information drawingmeans 109 draws the intersections by varying the colors and the patternsthereof in accordance with the range of the travel times (e.g., therange accessible within 5 minutes, the range accessible within 5 to 10minutes) to access the intersections, without drawing isochronal linesnor isochronal zones. Further, the time information drawing means 109may draw landmarks displayed on the map, by varying the colors and thepatterns thereof. Furthermore, the time information drawing means 109may obtain the isochronal lines of the drawing style (1) by determining,based on image processing performed for the intersections represented byvarying the colors and the patterns thereof, the boundaries between thecolors and the boundaries between the patterns.

Although the function, performed by the time information drawing means109, of determining a drawing style of the travel time information andof displaying the determined drawing style with the map information onthe display means 105 is described above, the drawing styles (1) through(3) may be used in a combined manner. For example, roads may be drawn byvarying the colors thereof in accordance with the travel times, whileisochronal lines and isochronal zones may be drawn for landmarks.

Further, it is possible to draw the travel time information more simplyin the above-described manner than to draw the travel time informationby representing traffic information as a local collection of arrows in aconventional manner, and therefore is possible to avoid the user'sconfusion. Thus, it is safe to view the travel times (trafficinformation) while driving.

Next, with reference to FIGS. 18 through 20, the function, performed bythe time information drawing means 109, of controlling a display form inaccordance with the scale and the vehicle speed so as to improve thevisibility of the displayed travel time information will be describedtaking isochronal lines as an example.

FIG. 18 is a schematic diagram showing a state where the intervalsbetween the travel times indicated by isochronal lines are changed inaccordance with the scale of a displayed map. When a detailed map havinga large scale (the scale of 800 m in the figure) is displayed as shownin (A) of FIG. 18, the travel times to points provided within thedisplayed ranges are short, and therefore isochronal lines are drawn toindicate 5-minute intervals. In contrast, when a wide-area map having asmall scale (the scale of 6.4 km in the figure) is displayed as shown in(B) of FIG. 18, the travel times are long, and therefore isochronallines are drawn to indicate 15-minute intervals. The reason is thatsince a large number of isochronal lines would be required to be drawnif drawn to indicate 5-minute intervals, the visibility would be low.The intervals between the travel times indicated by the isochronal linesmay be changed depending on the scale as described above, and thus it ispossible to draw appropriate isochronal lines determined in accordancewith the displayed area.

FIG. 19 is a flow chart showing an operation, illustrated in FIG. 18, ofcontrolling a display form in accordance with the scale so as to improvethe visibility of the displayed travel time information. In FIG. 19,first, the time information drawing means 109 determines whether or notisochronal lines are drawn in a superimposed manner on the map (stepS41). When the isochronal lines are not drawn in a superimposed manneron the map (step S41: “No”), the time information drawing means 109returns to prior to step S41. When the isochronal lines are drawn in asuperimposed manner on the map (step S41: “Yes”), the time informationdrawing means 109 proceeds to step S42. In step S42, the timeinformation drawing means 109 determines whether or not the scale of themap has been changed. When the scale of the map has not been changed(step S42: “No”), the time information drawing means 109 returns toprior to step S41. When the scale of the map has been changed (step S42:“Yes”), the time information drawing means 109 proceeds to step S43. Instep S43, the time information drawing means 109 controls the intervalsbetween the travel times indicated by the isochronal lines (the widerthe area, the longer the intervals). Note that although in FIGS. 18 and19, described is interval control of the isochronal lines which isperformed when the scale is changed by the user, the present inventionis not limited thereto. The number of isochronal lines displayed on onescreen may be a constant number (e.g., three) and the scale may beautomatically changed such that all of the constant number of theisochronal lines are included in the one screen. Further, even when thescale is of the same, the intervals between the travel times may bechanged in accordance with the vehicle speed or with the degree oftraffic congestion.

FIG. 20 is a flow chart showing an operation of controlling, even whenthe scale is of the same, a display form in accordance with the vehiclespeed so as to improve the visibility of the displayed travel timeinformation. In FIG. 20, first, the time information drawing means 109determines whether or not isochronal lines are drawn in a superimposedmanner on the map (step S51). When the isochronal lines are not drawn ina superimposed manner on the map (step S51: “No”), the time informationdrawing means 109 returns to prior to step S51. When the isochronallines are drawn in a superimposed manner on the map (step S51: “Yes”),the time information drawing means 109 proceeds to step S52. In stepS52, the time information drawing means 109 determines whether or notthe vehicle speed acquired by the position determining means 103 hasbeen changed. When the vehicle speed has not been changed (step S52:“No”), the time information drawing means 109 returns to prior to stepS51. When the vehicle speed has been changed (step S52: “Yes”), the timeinformation drawing means 109 proceeds to step S53. In step S53, thetime information drawing means 109 controls the intervals between thetravel times indicated by the isochronal lines in accordance with thevehicle speed (the slower the vehicle speed, the longer the intervals).The reason for the above control will be described. Take for example thetravel times to points provided within the map range displayed at somepoint in time: when the vehicle speed is slow due to traffic congestionor the like, it takes longer times to access the points than it does atthe ordinary vehicle speed. And since more isochronal lines would bedrawn in the case of traffic congestion or the like if the intervalsbetween the travel times indicated by isochronal lines were constant,the visibility would be low. In contrast, it may be set that the fasterthe vehicle speed, the shorter the intervals, and thus it is possible toappropriately control the number of isochronal lines to be drawn.

Next, with reference to FIGS. 21 and 22, the function, performed by thetime information drawing means 109, of performing a drawing effect willbe described taking isochronal lines as an example.

FIG. 21 is an example where isochronal lines to be drawn aresequentially changed so as to radiate from an isochronal line of theshorter travel time to an isochronal line of the longer travel time. InFIGS. 12 and 18, only the isochronal lines of the discrete travel times(e.g., 10-minute travel time, 15-minute travel time) can be drawn, sincethe isochronal lines are statically drawn (the reason is that since thedensity of the isochronal lines would be high if the isochronal lineswere successively drawn, the visibility would be low). However, as shownin FIG. 21, isochronal lines may be drawn to radiate by sequentiallystopping the isochronal lines of the shorter travel times from beingdisplayed, and thus it is possible to display the isochronal lines of asuccessive and small unit, such as 10-minute travel time, 11-minutetravel time, and 12-minute travel time, in an easily understandablemanner. Further, the isochronal lines sequentially drawn may appeal tothe eye of the user, and consequently, the isochronal lines can also behighlighted. Furthermore, when the isochronal lines sequentially changedso as to radiate have radiated outside the map having the current scale,the scale may be switched to that of a wider area.

Further, as shown in FIG. 22, isochronal lines of the longer traveltimes may be sequentially drawn while isochronal lines of the shortertravel times remain displayed. Alternatively, isochronal lines may bedisplayed by setting a standard that the difference between the shortestand longest travel times indicated by isochronal lines is less than acertain value (when the difference is set as 10 minutes, if theisochronal lines of 5-minute travel time, 10-minute travel time, and15-minute travel time are drawn at certain timing, the isochronal linesof 10-minute travel time, 15-minute travel time, and 20-minute traveltime are drawn at the next timing).

Further, isochronal lines may be drawn using colors (5-minute traveltime in blue, 10-minute travel time in yellow, 15-minute travel time inred, etc.) different from one another and patterns (a solid line, adashed line, a chain line, etc.) different from one another.Furthermore, when a plurality of isochronal lines are displayed, thethicknesses of each several isochronal lines thereof may be changed.

Further, a drawing effect may be performed for a map area displayedwithin a predetermined isochronal line in a different manner than thatperformed for a map area displayed outside the predetermined isochronalline. For example, in display as shown in FIG. 12, the outer map areaprovided outside the outermost isochronal line, which is of 20-minutetravel time, may be filled in white or black or may be applied with atransparent texture, so as to be more difficult to view than the innermap area is. That is, the user can pay attention to the inner map area.Note that the above-described process may be performed not for theoutermost isochronal line but for another arbitrary isochronal line.

Although the function, performed by the time information drawing means109, of performing a drawing effect is described above, the drawingstyles (1) through (3) and the drawing effect may be used in a combinedmanner.

Next, with reference to FIG. 23, the function, performed by the timeinformation drawing means 109, of changing, when receiving from the useran instruction to change a travel time, the travel time to an arbitrarytravel time will be described.

FIG. 23 is a schematic diagram showing the function of changing, whenreceiving from the user an instruction to change a travel time, thetravel time to an arbitrary travel time. In FIG. 23, the display means105 includes an input function such as a touch panel, such that anisochronal line displayed thereon can be operated by the user and anisochronal line of an arbitrary travel time can be displayed in responsethereto.

(A) and (B) of FIG. 23 show an example where a displayed isochronal lineof 10-minute travel time is pressed and then slid remaining pressed, andthen indicates 15-minute travel time. It is to be understood that theisochronal line may be drawn to indicate the travel time of between 10minutes and 15 minutes, such that the isochronal lines of the traveltimes are successively drawn at arbitrary positions pressed by the user.Note that an effect of changing, when an isochronal line is pressed bythe user, the color of the isochronal line to the color of response, andthe like may be performed.

Further, in (C) and (D) of FIG. 23, a slider bar is displayed on ascreen, such that a slider thereof is moved left and right by the user,whereby an isochronal line of an arbitrary travel time can be drawn.Note that when the slider bar is displayed in an up/down direction in alongitudinal manner, the slider may be moved up and down. Apredetermined travel time may be instructed by an input through a remotecontrol and the like, as well as by an input through the touch panel asdescribed above.

Further, the scale of the range within a selected isochronal line may bechangeable. For example, the map may be reduced when the user presses anisochronal line and moves his/her finger in a direction of the searchstart position (the position of the user's vehicle in an example asshown in FIG. 23), while the map may be enlarged when the user moveshis/her finger in the opposite direction.

Next, with reference to FIG. 24, the function, performed by the timeinformation drawing means 109, of drawing/updating the travel timeinformation will be described. FIG. 24 is a flow chart showing anoperation, performed by the time information drawing means 109, ofdrawing/updating the travel time information.

In FIG. 24, first, the time information drawing means 109 determineswhether or not the travel time information is drawn in a superimposedmanner on the map (step S61). When the travel time information is notdrawn in a superimposed manner on the map (step S61: “No”), the timeinformation drawing means 109 returns to prior to step S61. When thetravel time information is drawn (step S61: “Yes”), the time informationdrawing means 109 proceeds to step S62. In step S62, the timeinformation drawing means 109 determines whether or not the position ofthe user's vehicle has passed through a node, whether or not apredetermined time (e.g., 1 minute) has passed, and/or whether or notthe traffic congestion information has been received. When thedetermination made in step S62 indicates “false” (step S62: “No”), thetime information drawing means 109 returns to prior to step S61. Whenthe determination made in step S62 indicates “true” (step S62: “Yes”),the time information drawing means 109 draws/updates the travel timeinformation (step S63).

Further, the time interval of drawing/updating the travel timeinformation may vary depending on the scale of a map. For example, theupdate time interval may be short in a detailed map having a largescale, since a change, based on the movement of the user's vehicle, ofan apparent position of the user's vehicle is large on the display means105. And the update time interval may be long in a wide-area map havinga small scale, since a change, based on the movement of the user'svehicle, of an apparent position of the user's vehicle is small on thedisplay means 105.

Next, with reference to FIG. 25, the function, performed by the timeinformation drawing means 109, of controlling arrow display indicatingtraffic congestion occurring on a road will be described. FIG. 25 is aflow chart showing an operation, performed by the time informationdrawing means 109, of controlling arrow display indicating trafficcongestion occurring on a road.

In FIG. 25, first, the time information drawing means 109 determineswhether or not the travel time information is drawn in a superimposedmanner on the map (step S71). When the travel time information is notdrawn in a superimposed manner on the map (step S71: “No”), the timeinformation drawing means 109 returns to prior to step S71. When thetravel time information is drawn in a superimposed manner on the map(step S71: “Yes”), the time information drawing means 109 proceeds tostep S72. In step S72, the time information drawing means 109 controlsarrow display indicating traffic congestion occurring on a road. Thus,it is possible to display the travel times in lieu of displaying trafficinformation in a conventional manner. It is possible to prevent a mapdisplayed on a display screen from being complicated and disorganized,particularly when detailed traffic information including narrow streetsis available.

Next, with reference to FIG. 26, a function, performed by the timeinformation drawing means 109, of displaying the travel time informationin a radiating manner and of also displaying a recommended POI which ispresent in an isochronal zone indicated by the travel time informationwill be described. Note that it is assumed in this case that thetemporally closer the recommended POI is to the current position, thehigher the recommendation level of the recommended POI is.

FIG. 26 is a flow chart showing an operation, performed by the timeinformation drawing means 109, of displaying the travel time informationin a radiating manner and of also displaying a recommended POI which ispresent in an isochronal zone indicated by the travel time informationand which is temporally closest to the current position.

In FIG. 26, first, the time information drawing means 109 determineswhether or not an instruction to perform a search for a POI has beengiven (step S81). When the instruction has not been given (step S81:“No”), the time information drawing means 109 returns to step S81. Whenthe instruction has been given (step S81: “Yes”), the time informationdrawing means 109 proceeds to step S82. In step S82, the timeinformation drawing means 109 displays, in a radiating manner,isochronal zones each indicating the range accessible in a predeterminedtime.

Next, the time information drawing means 109 extracts, from thedisplayed isochronal zones, the POI temporally closest to the currentposition (step S83). Further, as shown in FIG. 27, the time informationdrawing means 109 displays, in a highlighted manner, the POI extractedin step S83 and also displays the route to the POI in a blinking manner(step S84). Next, the time information drawing means 109 determineswhether or not a predetermined number of (e.g., three) POI have beendisplayed (step S85).

When the predetermined number of POI have not been displayed, the timeinformation drawing means 109 returns to step S82 so as to repeat theprocess of steps S82 through S84. That is, the process is repeated,whereby as shown in FIGS. 27 through 30, first, an isochronal zoneaccessible in 5 minutes is displayed, a point A which is provided withinthe isochronal zone indicating the range accessible in 5 minutes andwhich is temporally closest to the current position is displayed in ahighlighted manner, and the route to the point A is displayed in ablinking manner. Next, an isochronal zone indicating the rangeaccessible in 10 minutes is displayed, a point B which is providedwithin the isochronal zone indicating the range accessible in 5 to 10minutes and which is temporally closest to the current position isdisplayed in a highlighted manner, and the route to the point B isdisplayed in a blinking manner. Next, an isochronal zone accessible in15 minutes is displayed, a point C which is provided within theisochronal zone indicating the range accessible in 10 to 15 minutes andwhich is temporally closest to the current position is displayed in ahighlighted manner, and the route to the point C is displayed in ablinking manner.

On the other hand, when the predetermined number of POI have beendisplayed, the time information drawing means 109 determines whether ornot an instruction to specify POI has been received from the user (stepS86). When the instruction to specify has not been received (step S86:“No”), the time information drawing means 109 waits until an input isreceived. When the instruction to specify has been received (step S86:“Yes”), the time information drawing means 109 displays a route guidanceto the specified POI (step S87).

Note that described is an example where it is assumed that thetemporally closer the recommended POI is to the current position, thehigher the recommendation level of the recommended POI is, such that therecommended POI are extracted in order of the temporal proximity to thecurrent position. The recommended POI, however, may be extracted inascending order of evaluation value obtained by performing weightedaddition on the distance from the current position, the travel time fromthe current position, and/or a value obtained by quantifying thedirection from the current position. Alternatively, the user's accesshistory of accessing POI may be stored, whereby, with reference to thestored user's access history, the recommended POI may be extracted indescending order of the frequency of accessing a POI.

As described above, based on the present invention, it is possible toprovide a map displaying device for displaying an accessible range in anarbitrary display form determined in accordance with the scale of adisplayed map and/or with the running state of a vehicle. That is, sincethe present invention displays, on an ordinary and familiar map, traveltime information represented by the travel time to an arbitrary pointand the travel time to travel between arbitrary points, in accordancewith the scale of a displayed map and with the running state of avehicle, it is possible to present to a user a geographical distance anda temporal distance in an easily understandable manner.

While the invention has been described in detail, the foregoingdescription is in all aspects illustrative and not restrictive. It is tobe understood that numerous other modifications and variations can bedevised without departing from the scope of the invention. Particularly,the map displaying device according to the present invention can also beused as a portable navigation device, a map displaying applicationdisplayed on a personal computer, and a car allocation/command system ofa taxi, a security company or the like. Further, the map displayingdevice according to the present invention can also be applied to othertraveling objects such as an aircraft, a ship, and a train.

INDUSTRIAL APPLICABILITY

A map displaying device according to the present invention is applicableto any device or system each capable of displaying a map and each ofwhich may include a navigation device, a personal computer, a mobilephone, and a car allocation/command system of a taxi, a security companyor the like.

1. A map displaying device comprising: a display means for displayingmap information stored in a map database; a search means for calculatingtravel time information regarding a travel time to an arbitrary pointaccessible from a reference point; and a time information drawing meansfor displaying, in a superimposed manner on a map displayed on thedisplay means, the travel time information by varying a display form inaccordance with a scale of the map and/or with a running state of auser's vehicle, wherein the time information drawing means displays, asa zone, the travel time information indicating a range accessible withina certain travel time or within a certain travel time period.
 2. The mapdisplaying device according to claim 1, wherein the time informationdrawing means displays, when displaying a plurality of the zones, theplurality of the zones by a gradation.
 3. The map displaying deviceaccording to claim 1, wherein the time information drawing meansdisplays the travel time information by drawing a road and/or anintersection in various display forms in accordance with the travel timeor a travel time period.
 4. The map displaying device according to claim1, wherein the time information drawing means displays the travel timeinformation by changing an interval between displayed travel times suchthat the interval becomes longer as the scale of the map becomes wider.5. The map displaying device according to claim 1, wherein the timeinformation drawing means displays the travel time information bysequentially drawing, in a radiating manner, travel times or travel timeperiods in accordance with large/small relationships among the traveltimes or among the travel time periods, respectively.
 6. The mapdisplaying device according to claim 1, wherein the time informationdrawing means displays the travel time information by performing drawingeffects different between an inside and an outside of a line indicatinga predetermined travel time or of a zone indicating a predeterminedtravel time period.